1. Field of the Invention
Embodiments of the present invention relate generally to systems for protecting signal transmission devices from adverse conditions that could alter operation of the signal transmission device, such as adverse environmental conditions including dirt, moisture, insects, local chemical and biological contaminants, and microorganisms. More particularly, embodiments of the present invention relate to the protection of a splice or other connection in a signal transmission device, such as an electrical or optical cable. Even more particularly, embodiments of the present invention relate to a novel closure for protecting splice connections from exposure to moisture or other environmental elements that may harm or otherwise interfere with operation of the signal transmission device.
2. Description of Related Art
Changes in plant construction philosophy and methods have often led to the need for new products. The telephone subscriber loop presents one such case. The initial deployment of buried drop wires envisioned a continuous, monolithic run between the terminal and the customer premises. It was expected that, due to the low cost of materials, faulty or faulted runs would be replaced rather than repaired. Today, with the high costs involved with disrupting existing landscaping, the practice of splicing buried drop wire has become common enough to require a special system to protect the integrity of the connection.
The initial distribution plant in coaxial cable used a mechanical connector that was thought to be weather resistant by design. Over the years, these connections have shown themselves to be prone to failure from water intrusion and corrosion. The protection of existing splice connections can require a xe2x80x9csplit sleevexe2x80x9d system that can be placed mid-span in an existing cable run. The complex geometry of the mechanical connector or connector/tap oftentimes requires the system to be capable of having an encapsulant that will penetrate thoroughly, exclude oxygen to reduce oxidative corrosion, exclude water to prevent signal degradation and electrolysis. A complete potting of the entire connection will help prevent the formation of differential aeration cells. Encapsulants should not exhibit any creep over time since these connections are often made in aluminum conductors and the aluminum can be prone to cold flow. Encapsulant entry could cause an increase in resistance that would lead to cable heating and signal loss at the potentials that are imposed on coaxial cable.
There are several types of systems used for the protection of a buried drop wire splice. The first kind of system uses a two part chemical system that is mixed in the field in a container that may also serve as the final closure. The wires are immersed in the container or the mixture may be poured over the wires in an additional enclosure. There is considerable worker and environmental exposure and hence, resistance to handling small chemical mixes in the field. They can be messy, difficult to handle and apply. There is also the related expense in time lost while waiting for the system to cure. In cold climates the time can be appreciable relative to the entire repair operation.
A second system uses a grease or polymeric filling material confined in a multi-part rigid closure. The joined wires and bonding are inserted in the closure and the parts manually pressed or mechanically forced together to distribute the filling material into all of the void spaces. This approach is vulnerable to the effects of temperature on the flow of filling compound and the volume of wirework placed. Also, quality of work is difficult to monitor since there is no indication of completeness of the interstitial fill. Historically, inadequate filling leaves these systems vulnerable to water ingress from without and via the core of the drop wire. They exhibit severely limited life spans relative to the 40 years expected of most outside plant equipment.
A third system involves a rubber, generally cylindrical, elongated tubular member the inside surface of which is coated with a sealant. The tubular member is secured around the splice with the sealant on the inside surface used to secure the tubular member to the splice and to itself. No filling material is used to encapsulate the splice and prevent the ingress of water from without and via the core of the drop wire.
A fourth system commonly used is a heat-shrinkable sleeve. In addition to requiring special heating tools, there is the potential for deterioration of the integrity of the material due to overheating. Also, the available heat shrinkable materials for such applications are typically of high durometer to withstand the hostile environment, making re-entry as by slitting more difficult and limiting the flexibility of the spliced area. It is for these reasons that heat shrinkable materials have found little acceptance in the coaxial plant as well.
The nature of the mechanical connectors used in coaxial plant may necessitate periodic adjustment of the connector. Hence, any protective device must be easily removed and replaced. An advantage is gained if the same device can be reused as in the case where the encapsulant gel would return into the storage media leaving the connector clear and clean.
In the case of optical fibers, the present systems use large closures to house splices and provide mechanical strain relief and fiber alignment against micro bending losses. The use of mechanical connectors for fiber connections will increase as wider use of fiber is made in distribution plant and single fibers, rather than bundles or cables, are brought to the end use point. These connections will require protection from many environments from the weather to industrial environments on the factory floor to ordinary housekeeping activities in offices. The constant rearrangement of devices will require a protective device that is easily removed and that removes cleanly.
Splice protection systems of the present invention are useful for preventing unwanted entry of external elements into the splice regions of signal transmission devices, thus preserving the integrity and function of the signal transmission devices. In addition, embodiments of the present invention relate to closures for protecting signal transmission devices from adverse environmental conditions such as dirt, moisture, chemical contaminants and microorganisms that may adversely affect the operation of the signal transmission device. The adverse effects of dirt and moisture are of concern especially when the signal transmission devices are buried underground or placed in contaminated micro environments such as machine tool housings.
The protective sheathing or other coating (collectively xe2x80x9ccoatingxe2x80x9d) of signal transmission devices, such as electrical or optical cables, are oftentimes opened to fix the conductors, i.e. wires or optical fibers, therein or otherwise splice additional signal transmission devices together. Once the integrity of the protective coating is breached, dirt and moisture will penetrate the signal transmission device oftentimes causing failure unless steps are taken to seal out dirt and moisture and restore the original integrity of the cable.
In its simplest embodiment, the closures of the present invention include a wrapper, such as a flexible sheet of plastic, in combination with a water resistant material deposited onto or otherwise connected, affixed or adhered to the preferably flexible wrapper. The flexible wrapper with the water resistant material is then wrapped around the desired portion of the signal transmission device, such as a splice, and the water resistant material is manually massaged into the splice connection. The massaging of the material may be accomplished using numerous methods, such as, for example, manually massaging the material or massaging the material using mechanical tools, such as pliers, compression rings, and the like. The water resistant material is typically disposed on the wrapper and acts to invasively fill any spaces or voids after the closure is wrapped around the signal transmission device. That is, after wrapping the closure around a splice portion of a signal transmission device, which connects two or more signal transmission wires or cables, the closure is compressed to force the water resistant material into the spaces surrounding the connection portion. The closure may comprise innumerable geometric shapes and dimensions, and the shape is preferably chosen such that the closure can envelope the splice area to encapsulate the splice region. One skilled in the art, given the benefit of this disclosure, will be able to select shapes and geometries suitable for use in wrapping splices of signal transmission devices.
According to one embodiment of the present invention, the water resistant material is retained within a flexible delivery device attached to the wrapper or backing sheet and from which water resistant material is forced. The delivery device acts to hold the water resistant material prior to wrapping and compression of the closure around the splice. The flexible wrapper is of sufficient dimensions to encircle or otherwise enclose the splice and, in certain embodiments, is impermeable to the migration of the encapsulant and/or is water resistant, water impermeable or water impenetrable. In certain embodiments, the delivery device is a porous material that retains the water resistant material or is one or more breakable packages, bags or beads or other container containing the water resistant material. The delivery device can be secured to the flexible wrapper using adhesives, epoxies, removable fasteners such as double-sided tape, Velcro(copyright), and the like. Also, the delivery device can be adhered to the flexible wrapper by the water resistant material itself that is contained within the delivery device. According to one embodiment, the water resistant material is self-healing, and the self-healing property of the material allows for the formation of a single mass of water resistant material with no paths for the ingress of water or other chemical or biological contaminants. That is, the water resistant material is chosen such that compression of the water resistant material results in occupancy of any and/or all spaces or cavities contained within the closure.
According to the present invention, the splice is surrounded by the closure and then the water resistant material is forced into and around the desired portion of the signal transmission device (such as a splice), according to one embodiment, by applying pressure to the closure and, if present, the delivery device, such as manual pressure or radial force applied by an over-wrapping, elastomeric media. The water resistant material encapsulates or otherwise surrounds the splice thereby restricting penetration of dirt and moisture into the splice and at a location where dirt and moisture can adversely affect the operation of the conductors in the signal transmission device. The user can determine the nature and extent of manual pressure, such as by squeezing by hand, needed to effectuate the desired amount of water resistant material required to surround the splice for adequate protection. The closure can be securely attached to the splice and also covered with a suitable water or other environmentally or mechanically resistant covering.
In accordance with preferred embodiments, the backing sheet or wrapper comprises a sheet of plastic, rubber, paper, metal, or other flexible material. Preferably, any material that is capable of being wrapped around a cylindrically shaped object, such as a electrical cables, coaxial cables, fiber optic cables, category 5 cables and the like, may be used in the backing sheet. Preferably the backing sheet or wrapper is a flexible, water impenetrable material such as polyethylene, polypropylene, rubber and the like. In certain embodiments, the water resistant material is retained within a flexible delivery device from which water resistant material is forced using compression. In preferred embodiments, the water resistant material is typically any suitable commercially available gel, grease or encapsulant that is used in the telecommunications industry as a water resistant material. Examples of such materials include commercially available lubricants and greases, such as those available from Nye Lubricants (New Bedford, Mass.). The water resistant material need not be formulated prior to application to the splice, such as is the case of commercially available two part mixtures. The water resistant material typically is ready for use as deposited on or otherwise connected to the flexible wrapper or as contained within the delivery device. The water resistant material may exit the delivery device by the application of pressure, heat, or other mechanical forces capable of forcing the water resistant material out of the delivery device.
In accordance with preferred embodiments, the delivery device typically comprises a porous structure suitable for retaining the water resistant material. Such porous structures typically have sponge-like properties yet have the ability to release the water resistant material if compressed. The delivery device may comprise numerous pores having similar or different sizes, geometries, and shapes. That is, the number, size, and geometries of the pores may vary depending on the intended use of the delivery device and on the properties and characteristics of the water resistant material to be disposed on or in the delivery device. Preferably, the delivery device comprises at least about 2 pores per square inch. More preferably the delivery device comprises about 4 to 50 pores per square inch. In certain embodiments, the pores preferably have a diameter of less than about 1 inch, more preferably less than about 0.5 inches, and most preferably less than about 0.1 inches, for example 0.01 inches or less. One skilled in the art, given the benefit of the disclosure, will be able to select suitable pore diameters and sizes depending on the properties and characteristics of the water resistant material.
In accordance with another aspect, a kit is provided that includes a closure, a water impervious covering and binders for securing the water impervious covering over the closure. The water impervious covering can be any commercially available rubber sleeve or wrapper and the binders can be commercially available tape such as butyl tape. Additional elements of the kit can include additional tapes, such as vinyl tape, clamps, cable ties and rigid enclosures into which the closure is placed. According to the present invention, the rigid enclosure can be fashioned from plastic, metal or other rigid material and encloses the splice protection system of the present invention.
In accordance with a method aspect, the closure is used to protect a signal transmission device from dirt and moisture by application of the closure to the splice area of the signal transmission device. The method typically comprises contacting and wrapping the splice with the closure and compressing the closure to force the water resistant material into voids in the splice. In certain embodiments, a user positions a splice on the delivery device and then positions the wrapper around the splice. The user then applies manual pressure to force the water resistant material from the delivery device as the wrapper is folded around the splice. The user then secures the closure around the splice using tape while continually applying pressure to the closure, for example manually massaging the closure, in a manner to provide for maximum distribution of the water resistant material around and into the splice. The water resistant material advantageously maintains its properties regardless of the ambient temperature. Tactile feedback to the user aids in determining the completeness of the fill of the water resistant material around the splice. The closure may then be secured to the signal transmission device using any of the methods and apparatus described here or other suitable methods known to those skilled in the art.
Unlike prior, conventional two part systems that require the user to mix separate solutions to create the gel used to encapsulate the splice, the closure of the present invention is particularly advantageous because premixing of the water resistant material is not required by the user. The present invention avoids the difficulties of having to mix chemical ingredients in the field and also eliminates the use of a separate container that surrounds the splice and into which the mixed chemical system is poured. Also, certain embodiments of the present invention prevent any unnecessary hand or component contact with the water resistant material during application.
Accordingly, it is an object of the present invention to provide a simple and easy to use system for the protection of a signal transmission device from adverse environmental conditions such as dirt and moisture. It is another object of the present invention to provide a closure for a splice of a signal transmission device to protect the splice from adverse environmental conditions such as dirt and moisture. It is yet another object of the present invention to provide a system for the protection of a splice that is directly buried underground or is in an underground plant. It is still yet another object of the present invention to provide a system for the protection of a splice that uses a water resistant material that need not be premixed prior to application to the splice. It is a further object of the invention to provide a system for the protection of a splice that allows for easy determination of completeness of fill prior to burial.
These and other objects, features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.